Brobdignagian is a word that describes something that is unusually large. However, it is not a very commonly used term in everyday conversation. If you want to describe something as big, you can use synonyms like gigantic, massive, colossal, and mammoth. If you want to describe something as even bigger than these words, you can use terms like astronomical or monumental. Other synonyms for brobdignagian are prodigious, humongous, enormous, and towering. If you want to describe something as being impressively large but not necessarily in a physical sense, you could use terms like monumental or epic. Ultimately, there are plenty of words that you can use to describe something that is brobdignagian without actually using that particular term.